A key part of printers and other conventional image-sensor devices is the Contact Image Sensor (CIS) scan bar, which transforms an image on paper into an electronic image. A CIS scan bar may be widely used for facsimile (fax) machines, optical scanners, and portable applications e.g. portable scanners.
Over the years, the cost of CMOS imaging-sensor arrays has decreased, and their performance level increased: these sensors may thus be used in the place of conventional CIS scan bars, giving rise to cheaper solutions without any adverse impact on scanner size.
Different solutions have been proposed in order to use CMOS/CCD imaging-sensor arrays to scan a document.
For instance, DE-A-102006010776, which is incorporated by reference, discloses an arrangement including four fixed CCD-sensors, which are located under a glass for supporting the documents to be scanned and which operate on the basis of a pre-calibrated evaluation algorithm to form an entire image.
Various documents disclose different kinds of image-sensor carriages for mounting image reading means in combination with a drive unit (driving motor) to move the carriage.
For instance, GB-A-2336734, which is incorporated by reference, discloses an image sensor arranged parallel to the short sides of a rectangular lower frame to capture the image of a scanned object placed on a transparent plate mounted on a rectangular upper frame. A rod-like guiding member is provided orthogonal to the longitudinal holder to guide the movement of the image sensor.
In the solution disclosed in JP-A-2005331533, which is incorporated by reference, an image scanner is equipped with a carriage on which an image sensor is mounted. A driving motor moves the carriage in a sub-scanning direction via a toothed timing belt.
US-A-2006/098252, which is incorporated by reference, discloses a drive device for a scanner which includes an elongate guiding unit mounted in a base and disposed under an image sensor carriage. A roller unit is mounted on a bottom side of the image sensor carriage and a driving unit drives the image sensor carriage in a second direction with respect to the base.
Documents such as US-A-2008/174836 and JP-A-20060245172, which are incorporated by reference, disclose a scanner device adapted to scan an object and generate image data; the scanner device includes an image sensor and a movement unit which moves in a sub-scan direction a carriage carrying the image sensor.
EP-A-0 886 429, which is incorporated by reference, discloses an image input/output apparatus capable of printing and reading images and a cartridge carriage for reading an original with a simple control: the system uses a camera module which replaces the ink cartridge, sharing the same circuitry, which may turn out to be critical for maintaining the same speed for printing and as regards manual replacement of the cartridges.
Document CN-A-201286132, which is incorporated by reference, discloses a planar-image sensor, high-speed scanner with a reading function, and a copying machine containing an image part, at the bottom of a workbench, which includes n sets of image detection parts and a set of image reading parts; a light-source part above the image part; and a reflection part above the light-source part. A main drawback of this solution may lie in that too many cameras may be needed to cover the entire document area.
Document US-A-2009/0021798, which is incorporated by reference, discloses a scanner operating system with a single camera module. Such an arrangement is implemented in an “All-in-One” (AiO) product traded by Lexmark® under the commercial designation Genesis, which uses a single fisheye lens. A main drawback of this arrangement lies in the negative impact on system height.
In brief, the idea of using one or more sensors (fixed or in motion) to scan an image (or part of an image) has been largely adopted. If the image sensor is intended to be moved in operation, these arrangements almost inevitably involve the use of an additional carriage for the sensor.